Image-capturing apparatus, accessory apparatus and control method therefor

1. An image-capturing apparatus to which an accessory apparatus is attachable, the image-capturing apparatus comprising: a memory that stores instructions; and a camera controller configured to execute the instructions stored in the memory to receive first data via a first communication channel and to transmit second data via a second communication channel, wherein the camera controller is configured to perform communication by a first communication mode and a second communication mode, wherein the first communication mode is a communication mode where the camera controller (a) receives the first data in accordance with a change of signal level of a third communication channel from a first signal level to a second signal level and (b) transmits the second data in accordance with the reception of the first data, wherein the second communication mode is a communication mode where the camera controller (a) receives the first data in accordance with maintenance of the third communication channel at the second signal level after the change of signal level of the third communication channel from the first signal level to the second signal level and (b) transmits the second data in accordance with the reception of the first data, and wherein setting of a parity bit of the first data in the first communication mode and setting of a parity bit of the first data in the second communication mode are different.

2. An image-capturing apparatus according to claim 1 , wherein the setting of a parity bit of the first data in the first communication mode and the setting of a parity bit of the first data in the second communication mode are different in that the parity bit is added or not added or in that the parity bit indicates even parity or odd parity.

3. An image-capturing apparatus according to claim 1 , wherein the parity bit in one of the first and second communication modes indicates even parity or odd parity, and the parity bit in the other thereof is not included.

4. An image-capturing apparatus according to claim 1 , wherein the camera controller is configured to detect a parity error of the first data and thereby detect a difference in communication mode between the camera controller and the accessory apparatus.

5. An image-capturing apparatus according to claim 4 , wherein the camera controller is configured to perform, in response to detecting the difference in communication mode, a matching process for matching the communication modes of the camera controller and the accessory apparatus.

6. An image-capturing apparatus according to claim 5 , wherein the camera controller is configured to perform, in response to detecting the difference in communication mode when the communication mode of the camera controller is the first communication mode, the matching process that changes the communication mode of the accessory apparatus to the first communication mode.

7. An image-capturing apparatus according to claim 5 , wherein the camera controller is configured to perform, in response to detecting the difference in communication mode when the communication mode of the camera controller is the second communication mode, the matching process that changes the communication mode of the camera controller to the first communication mode.

8. An image-capturing apparatus according to claim 1 , wherein the camera controller is configured to perform asynchronous communication with the accessory apparatus, and wherein the camera controller is configured to output a signal via the third communication channel.

9. An image-capturing apparatus according to claim 8 , wherein the camera controller is configured to: in the first communication mode, receive from the accessory apparatus the first data to which a communication standby request is added; in the second communication mode, receive from the accessory apparatus the first data to which the communication standby request is not added; in the first communication mode, not provide a communication request until the communication standby request is terminated; and in the second communication mode, continue providing the communication request to the accessory apparatus by the maintenance of the third communication channel at the second signal level until the communication of a predetermined amount is performed, and switch, in response to completion of the communication of the predetermined amount, the communication mode of the camera controller to the first communication mode.

10. An image-capturing apparatus according to claim 8 , wherein the camera controller is configured to perform, in response to detecting a difference in communication mode in the first communication mode, a matching process that does not provide the communication request for a predetermined time and thereby switches the communication mode of the accessory apparatus to the first communication mode.

11. An accessory apparatus attachable to an image-capturing apparatus, the accessory apparatus comprising: a memory that stores instructions; and an accessory controller configured to execute the instructions stored in the memory to transmit first data via a first communication channel and to receive second data via a second communication channel, wherein the accessory controller is configured to perform communication by a first communication mode and a second communication mode, wherein the first communication mode is a communication mode where the accessory controller (a) transmits the first data in accordance with a change of signal level of a third communication channel from a first signal level to a second signal level and (b) receives the second data in accordance with the reception of the first data, wherein the second communication mode is a communication mode where the accessory controller transmits the first data in accordance with maintenance of the third communication channel at the second signal level after the change of signal level of the third communication channel from the first signal level to the second signal level, and wherein setting of a parity bit of the first data in the first communication mode and setting of a parity bit of the first data in the second communication mode are different.

12. An accessory apparatus according to claim 11 , wherein the setting of a parity bit of the first data in the first communication mode and the setting of a parity bit of the first data in the second communication mode are different in that the parity bit is added or not added or in that the parity bit indicates even parity or odd parity.

13. An accessory apparatus according to claim 11 , wherein the parity bit in one of the first and second communication modes indicates even parity or odd parity, and the parity bit in the other thereof is not included.

14. An accessory apparatus according to claim 11 , wherein the accessory controller is configured to switch the communication mode of the accessory controller, in response to receiving a switch request that requests switching the communication mode on the detection of a parity error of the first data.

15. An accessory apparatus according to claim 14 , wherein the accessory controller is configured to switch, in response to receiving the switch request on the detection of the difference in communication mode in the first communication mode, the communication mode of the accessory controller to the first communication mode.

16. An accessory apparatus according to claim 11 , wherein the accessory controller is configured to perform asynchronous communication with the image-capturing apparatus, and wherein the camera controller is configured to output a signal via the third communication channel.

17. An accessory apparatus according to claim 16 , wherein the accessory controller is configured (a) to transmit, in the first communication mode, the first data to which a communication standby request that requests prohibiting the image-capturing apparatus from providing the communication request is added, and (b) to transmit, in the second communication mode, the first data to which the communication standby request is not added while the communication request is provided from the image-capturing apparatus.

18. An accessory apparatus according to claim 16 , wherein the accessory controller is configured to perform, in response to not receiving the communication request for a predetermined time from the image-capturing apparatus that detects in the first communication mode a difference in communication mode, a switching process that switches the communication mode of the accessory controller to the first communication mode.

19. An accessory apparatus according to claim 11 , wherein the accessory controller is configured to transmit, in response to detecting abnormality of image-capturing apparatus data, the first data produced so as to cause the image-capturing apparatus to detect a parity error.

20. An image-capturing system including an image-capturing apparatus and an accessory apparatus attachable to the image-capturing apparatus, the system comprising: a memory that stores instructions; and a camera controller and an accessory controller configured to execute the instructions stored in the memory, the camera controller being included in the image-capturing apparatus and the accessory controller being included in the accessory apparatus, the camera controller being configured to receive first data via a first communication channel and to transmit second data via a second communication channel, and the accessory controller being configured to transmit the first data via the first communication channel and to receive the second data via the second communication channel, wherein the camera controller and the accessory controller are configured to perform communication by a first communication mode and a second communication mode, wherein the first communication mode is a communication mode where the camera controller (a) receives the first data in accordance with a change of signal level of a third communication channel from a first signal level to a second signal level and (b) transmits the second data in accordance with the reception of the first data, wherein the second communication mode is a communication mode where the camera controller (a) receives the first data in accordance with maintenance of the third communication channel at the second signal level after the change of signal level of the third communication channel from the first signal level to the second signal level and (b) transmits the second data according to the reception of the first data, and wherein setting of a parity bit of the first data in the first communication mode and setting of a parity bit of the first data in the second communication mode are different.

21. A control method of controlling an image-capturing apparatus to which an accessory apparatus is attachable, the control method comprising the steps of: receiving first data via a first communication channel and transmitting second data via a second data communication channel, wherein the control method is configured to perform communication by a first communication mode and a second communication mode, wherein the first communication mode is a communication mode where (a) the first data is received in accordance with a change of signal level of a third communication channel from a first signal level to a second signal level and (b) the second data is transmitted in accordance with the reception of the first data, wherein the second communication mode is a communication mode where (a) the first data is received in accordance with maintenance of the third communication channel at the second signal level after the change of signal level of the third communication channel from the first signal level to the second signal level and (b) the second data is transmitted in accordance with the reception of the first data, and wherein setting of a parity bit of the first data in the first communication mode and setting of a parity bit of the first data in the second communication mode are different.

22. A control method of controlling an accessory apparatus attachable to an image-capturing apparatus, the control method comprising the steps of: transmitting first data via a first communication channel and receiving second data via a second communication channel, wherein the control method is configured to perform communication by a first communication mode and a second communication mode, wherein the first communication mode is a communication mode where (a) a camera controller in the image-capturing apparatus receives the first data in accordance with a change of signal level of a third communication channel from a first signal level to a second signal level and (b) transmits the second data in accordance with the reception of the first data, wherein the second communication mode is a communication mode where (a) the camera controller receives the first data in accordance with maintenance of the third communication channel at the second signal level after the change of signal level of the third communication channel from the first signal level to the second signal level and (b) transmits the second data in accordance with the reception of the first data, and wherein setting of a parity bit of the first data in the first communication mode and setting of a parity bit of the first data in the second communication mode are different.

23. An image-capturing apparatus according to claim 1 , wherein the camera controller is configured to transmit, in the first and second communication modes, a request to the accessory apparatus to transmit the first data whose setting of a parity bit is predetermined so as to be different depending not on the first data, but on a communication mode of the accessory apparatus among the first and second communication modes.

24. An accessory apparatus according to claim 11 , wherein the accessory controller is configured to transmit, in the first and second communication modes, to the image capturing apparatus, the first data whose setting of a parity bit is predetermined so as to be different depending not on the first data, but on the communication mode of the accessory controller.

25. An image capturing apparatus according to claim 1 , wherein, in the second communication mode, the camera controller continues the reception of the first data during the maintenance of the third communication channel at the second signal level.

26. An image capturing apparatus according to claim 1 , wherein, in the second communication mode, the camera controller stops the reception of the first data in accordance with a change of signal level of the third communication channel from the second level to the first level, after the maintenance of the third communication channel at the second signal level.

27. An image capturing apparatus according to claim 1 , wherein, in the setting of the parity bit in the first communication mode, the parity bit indicates even parity or odd parity, and wherein in the setting of the parity bit in the second communication mode, the parity bit is not included.

28. An image capturing apparatus according to claim 1 , wherein the parity bit follows the first data, the first data consisting of a start bit of a third signal level and following 8 bit data.

29. An image capturing apparatus according to claim 28 , wherein a signal level of the first communication channel after the parity bit is a fourth signal level which is a different signal level than the third signal level.

30. An image capturing apparatus according to claim 29 , wherein, in the first communication mode, a stop bit of the fourth signal level follows the parity bit, and wherein, in the second communication mode, a stop bit of the fourth signal level follows the 8 bit data.

31. An accessory apparatus according to claim 11 , wherein, in the second communication mode, the accessory controller continues the transmission of the first data during the maintenance of the third communication channel at the second signal level.

32. An accessory apparatus according to claim 11 , wherein, in the second communication mode, the accessory controller stops the transmission of the first data in accordance with a change of signal level of the third communication channel from the second level to the first level, after the maintenance of the third communication channel at the second signal level.

33. An accessory apparatus according to claim 11 , wherein in the setting of the parity bit in the first communication mode, the parity bit indicates even parity or odd parity, and wherein in the setting of the parity bit in the second communication mode, the parity is not included.

34. An accessory apparatus according to claim 11 , wherein the parity bit follows the first data, the first data consisting of a start bit of a third signal level and following 8 bit data.

35. An accessory apparatus according to claim 34 , wherein a signal level of the first communication channel after the parity bit is a fourth signal level which is a different signal level than the third signal level.

36. An accessory apparatus according to claim 35 , wherein, in the first communication mode, a stop bit of the fourth signal level follows the parity bit, and wherein, in the second communication mode, a stop bit of the fourth signal level follows the 8 bit data.

37. An accessory apparatus according to claim 11 , wherein, in the second communication mode, the accessory controller receives the second data in accordance with the transmission of the first data.

38. An accessory apparatus according to claim 11 , wherein the accessory controller is configured to: in the first communication mode, not receive a communication request until a communication standby request is terminated; and in the second communication mode, continue receiving the communication request from the image-capturing apparatus in accordance with the maintenance of the third communication channel at the second signal level until the communication of a predetermined amount is performed.

39. An accessory apparatus according to claim 11 , wherein in the first communication where the accessory controller receives the second data in accordance with the transmission of the first data, the accessory controller receives the second data which is transmitted by the image-capturing apparatus in response to reception by the image-capturing apparatus of the first data that was transmitted by the accessory controller.